Borreliosis is caused by two groups of Borrelia, the B. borgdorferi group and the Tick-Borne Relapsing Fever (TBRF) Borrelia group. It was believed that the B. borgdorferi group was the only group that caused Lyme-like symptoms in infected subjects. However, it has been learned that TBRF Borrelia also causes Lyme-like symptoms. TBRF Borrelia is transmitted by hard (Ixodes) and soft (Ornithodorus) ticks.
Borrelia bacteria that cause TBRF are typically transmitted to humans through the bite of infected “soft ticks” of the genus Ornithodorus. Soft ticks differ in two important ways from the more familiar “hard ticks” (e.g., the dog tick and the deer tick). First, the bite of soft ticks is brief, usually lasting less than half an hour. Second, soft ticks do not search for prey in tall grass or brush. Instead, they live within rodent burrows, feeding as needed on the rodent (for example, squirrels, chipmunks and prairie dogs) as it sleeps.
The main symptoms of TBRF are high fever (e.g., 103° F.), headache, muscle and joint aches. Symptoms can reoccur, producing a telltale pattern of fever lasting roughly 3 days, followed by 7 days without fever, followed by another 3 days of fever. Without antibiotic treatment, this process can repeat several times.
Humans typically come into contact with soft ticks when they sleep in rodent-infested cabins. The ticks emerge at night and feed briefly while the person is sleeping. The bites are painless, and most people are unaware that they have been bitten. Between meals, the ticks may return to the nesting materials in their host burrows.
There are several Borrelia species that cause TBRF, and these are usually associated with specific species of ticks. For instance, B. hermsii is transmitted by O. hermsi ticks, B. parkerii by O. parkeri ticks, and B. turicatae by O. turicata ticks. Each tick species has a preferred habitat and preferred set of hosts.
Soft ticks can live up to 10 years. Individual ticks will take many blood meals during each stage of their life cycle, and some species can pass the infection along through their eggs to their offspring. The long life span of soft ticks means that once a cabin or homestead is infested, it may remain infested unless steps are taken to find and remove the rodent nest.
Since TBRF can be caused by several species of Borrelia, tests need to be comprehensive by including all known species. Also, identification of the Borrelia species can aid in identifying the host rodent for eradication. Currently, the standard for identification is by identification of TBRF spirochetes in blood smears of a subject presenting symptoms consistent with TBRF. After obtaining the blood draw the sample must be cultured for at least 24 hours to facilitate identification. However, even early in the disease when spirochetes are highest, positive identification is only made about 70% of the time. (See, www.cdc.gov/relapsing-fever/clinicians/index.html). Thus, prior art materials and methods result in a delay in diagnosis and provide a relatively low level of sensitivity and specificity.
Therefore, what is needed are new materials and methods suitable for the identification of TBRF causative agents with decreased assay time and increased sensitivity and specificity.